Such a related art switching device is constructed so that an operational button made of transparent synthetic resin, on which a character string, a sign, or the like is marked, is secured to a surface of a shaking plate, an assembly in which a side of the shaking plate is supported by a holder via a hinge formed of an elastic piece so that the shaking plate can shake is built into a face panel of vehicle-mounted audio equipment, the operational button is exposed to the cabin of a vehicle via an opening formed in the face panel, a projecting portion used for driving the switching device is formed on a back surface of the shaking plate and on another side of the shaking plate, and a light source for illuminating the operational button and a switch which is driven when pressed by the projecting portion used for driving the switching device are arranged behind the back surface of the operational button.
Next, the operation of the related art switching device will be explained.
The operational button is always illuminated directly by the light source, and, when the operational button is pushed in order to drive the switching device, the shaking plate shakes while being inclined somewhat because one side of the shaking plate is supported by the hinge, and the projecting portion disposed on the other side of the shaking plate presses and drives the switch.
In accordance with patent reference 1 which discloses a related art, there is provided a pushbutton switch for use in elevators, including a key-top portion attached to a wall surface so that it is exposed at least the surface of the wall, a light guiding plate secured to this key-top portion, for reflecting light incident thereupon toward the key-top portion, a buffer mechanism for supporting the key-top portion and the light guiding plate so that they can always move in parallel to the surface of the wall, a light emitting unit for applying light to a lateral surface of the light guiding plate which is placed opposite to the lateral surface of the light guiding plate, a switching body for bringing the light emitting unit into a lighting state when the light guiding plate is brought into contact therewith, and a circuit board on which this switching body, the light emitting unit, and a guide member are arranged, a contact surface of the light guiding plate being in contact with the switching body and serving as a reflecting surface for reflecting the light from the light emitting unit toward the key-top portion.
Patent reference 1: JP,2003-252538,A
Since the operational button is directly illuminated by the light source arranged in the back thereof in the related art switching device, the light emitted out of the light source does not spread while unevenness develops in the brightness of the surface of the operational button when the distance between the operational button and the light source is too short. It is necessary to leave some distance between the operational button and the light source, which is enough to prevent the operational button from being in contact with the light source when the operational button is pushed. A problem with the related art switching device is therefore that it is necessary to leave some distance between the operational button and the light source according to the two above-mentioned constraints, and hence the whole of the related art switching device increases in size.
A problem with the switching device disclosed in patent reference 1 is that since the light emitting unit is disposed on the lateral surface of the light guiding plate and hence the distance between the light guiding plate, which is integral with the key-top portion, and the light source changes as the key-top portion disposed as the operational button is pushed, the brightness of the key-top portion changes every time the key-top portion is operated.
The present invention is made in order to solve the above-mentioned problems, and it is therefore an object of the present invention to provide a switching device in which an operational button has brightness that does not change when pushed and has uniform brightness over the whole surface thereof and in which space saving is provided in order to achieve a downsizing of the whole of the switching device.